fix(amazonq): use String not ENUM for message communication

for some reason MessageType enum is not correctly parsed and will always return null when receiving from flare, change it to string so that the correct type is returned to correctly render history ask/answer texts.

Author: andrewyuq

plugins/amazonq/shared/jetbrains-community/src/software/aws/toolkits/jetbrains/services/amazonq/lsp/model/aws/chat/ChatMessage.kt

@@ -4,7 +4,7 @@
 package software.aws.toolkits.jetbrains.services.amazonq.lsp.model.aws.chat
 
 data class ChatMessage(
-    val type: MessageType? = MessageType.ANSWER,
+    val type: String? = MessageType.ANSWER.value,
     val header: MessageHeader? = null,
     val buttons: List<Button>? = null,
     val body: String? = null,